Temple is a wearable from Temple Wearables, founded by Deepinder Goyal after he left the Indian food delivery company Zomato. The device is a bean sized unit worn at the side of the head, where skin is thin, blood flow is high and little movement spoils a reading.

How it works

Light shines a short way into tissue and returns changed by the blood it met. A sensor at the temple reads that returning light to follow how much blood is reaching the brain and how much oxygen it carries. From those patterns the company derives a measure it calls Entropy, scored from 1 to 250, describing the metabolic and sympathetic effort of staying alive right then.

Key considerations

Entropy is the company's own measure with no outside validation, the device carries no regulatory clearance, and only a first cohort has shipped.